One of Britain’s harshest EU critics over Brexit is set to become German foreign minister and could challenge Angela Merkel for the chancellorship after he quit Brussels to return to national politics.

In a move that could have far-reaching consequences for the Brexit negotiations, Martin Schulz announced on Thursday he would not seek re-election as president of the European parliament.

While that will remove one of Brexit’s toughest opponents from the Brussels hierarchy, Mr Schulz is likely to have even more influence on negotiations from Berlin.

He is widely expected to be named German foreign minister early next year when the incumbent, Frank-Walter Steinmeier, takes over as German president.

And it is thought he may seek his party’s nomination to take on Mrs Merkel as chancellor in elections at the end of next year.

Martin Schulz, the European Parliament President, speaks during a news conference at the European Parliament in BrusselsCredit:
YVES HERMAN/Reuters

His decision to step down from the European parliament will also trigger a major shake-up in Brussels, and could threaten the position of Jean-Claude Juncker, the European Commission president.

“I will not run as president of the European parliament for a third term next year, I will run for the German Bundestag,” Mr Schulz said on Thursday.

“My commitment to the European project is unwavering. From now on I will be fighting for this project from the national level, but my values do not change.”

Proponents of a soft Brexit have been hopeful that Germany will take a pragmatic line in negotiations under Mrs Merkel.

But if Mr Schulz is appointed foreign minister that could change. The 60-year-old, has been one of the leading voices in Brussels calling for harsh terms for the UK’s withdrawal in order to discourage other members from leaving.

He has called for Britain to complete negotiations and leave by 2019, and warned that the UK cannot expect to cherrypick EU benefits such as access to the single market if it is not a member of the bloc.